Method For Sensing A Stylus On A Display Device And A Device For Sensing A Stylus

Abstract

The present invention relates to a method for sensing a stylus on a display device and a device for using the same. The display device has multiple sub-pixels and multiple common electrodes respectively corresponding to at least one of the sub-pixels. In the sensing stylus method, a signal of an active stylus is sensed through one of the common electrodes for displyaing an image in a displaying duration of the display device.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based upon and claims priority under 35 U.S.C. 119 from Taiwan Patent Application No. 106114159 filed on Apr. 27, 2017, which is hereby specifically incorporated herein by this reference thereto.

BACKGROUND OF THE INVENTION

1. Field of the Invention

[0002] The present invention relates to a touch display device, specifically related to a method for sensing an active stylus on a display device and a device for sensing an active stylus.

2. Description of the Prior Arts

[0003] An in-cell touch display device has a display panel with a common electrode layer. The common electrode layer is used as multiple touch sensing electrodes, so a time-division display-driving and touch-scanning method is employed for display driving and touch sensing. In the time-division display-driving and touch-scanning method, a duration (16.67 ms) of an image displaying period (1/60 Hz) of the display panel is divided into a displaying duration and a touch sensing duration. Since the touch sensing duration corresponds to a vertical blanking interval (VBI) of the display panel, an image displayed on the display panel is not affected by the touch sensing. During the displaying duration, the common electrode layer of the display panel is used to display an image. However, during the touch sensing duration, the common electrode layer is used to sense a touch object.

[0004] If the in-cell touch display device further adds a function of sensing an active stylus, the duration of the image displaying period has to be further divided into another duration to sense the active stylus. However, the duration of the image displaying period is fixed in general, which is 16.67 ms, the displaying duration has to be shortened if the touch sensing duration is prolonged to sense the active stylus. The image quality of the display panel may be affected accordingly. In another way, the displaying duration is maintained to keep a good image quality, but the time of sensing the touch object in the touch sensing duration has to be shortened and the rest time of the touch sensing duration is used to sense the active stylus. The accuracy of sensing the touch object is affected accordingly.

[0005] To overcome the shortcomings, the present invention provides a method for sensing an active stylus on a display device and a device for sensing an active stylus to mitigate or obviate the aforementioned problems.

SUMMARY OF THE INVENTION

[0006] Based on the aforementioned drawbacks of sensing the active stylus in the conventional time-division driving method, an objective of the present invention provides a method for sensing an active stylus on a display device and a device for sensing an active stylus.

[0007] To achieve the aforementioned objective, the present invention provides the method for sensing an active stylus on a display device. The display device has multiple sub-pixels and multiple common electrodes respectively corresponding to at least one of the sub-pixels. The method includes:

[0008] sensing a signal of an active stylus through one of the common electrodes for displaying an image in a displaying duration of the display device.

[0009] To achieve the aforementioned objective, the present invention provides a method for the device to sense an active stylus that is electrically connected to a display device. The display device has multiple sub-pixels, multiple common electrodes respectively corresponding to at least one of the sub-pixels and an image driving unit electrically connected to the sub-pixels. The device for sensing the active stylus has:

[0010] a touch sensing unit electrically connected to the common electrodes, wherein in a displaying duration of the display device, the image driving unit drives one of the sub-pixels to display an image and the touch sensing unit senses a signal of an active stylus through one of the common electrodes corresponding to the driven sub-pixel.

[0011] Based on the foregoing description, the present invention senses the active stylus during a display panel of the display device displays the image, but does not sense the active stylus in a touch sensing duration for sensing the touch object. As a result, the touch sensing duration is not prolonged to sense the active stylus so the quality of a displaying image is not decreased. Similarly, since the active stylus detection is not executed in the touch sensing duration, the accuracy of sensing the touch object is not affected.

[0012] Other objectives, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] FIG. 1 is a system schematic view of a display device in accordance with the present invention;

[0014] FIG. 2A is a structural schematic view of multiple sub-pixels and a common electrode layer of a first embodiment of a display device in accordance with the present invention;

[0015] FIG. 2B is a circuit diagram of one of the multiple common electrodes and a corresponding sensing unit in FIG. 2A;

[0016] FIG. 3A is a structural schematic view of multiple sub-pixels and a common electrode layer of a second embodiment of a display device in accordance with the present invention;

[0017] FIG. 3B is a circuit diagram of one of the multiple common electrodes and a corresponding sensing unit in FIG. 3A;

[0018] FIG. 4A is structural schematic view of multiple sub-pixels and a common electrode layer of a third embodiment of a display device in accordance with the present invention;

[0019] FIG. 4B is a circuit diagram of one of the multiple common electrodes and a corresponding sensing unit in FIG. 4A;

[0020] FIG. 5 is a time sequence diagram for the image display driving and touch sensing of the display device in accordance with the present invention;

[0021] FIG. 6A is a voltage waveform diagram showing voltage changes of a display signal of one of the multiple sub-pixels and the common electrode of the display device in accordance with the present invention;

[0022] FIG. 6B is a voltage waveform diagram showing voltage changes of the display signal of one of the multiple sub-pixels, the common electrode and a pixel electrode of the display device in accordance with the present invention; and

[0023] FIG. 7 is another circuit diagram of one of the multiple common electrodes and the corresponding sensing unit in FIG. 2A.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] The present invention provides a method and a device for sensing a stylus executed during an image displaying period. Many embodiments of the present invention are used to describe a detailed structure of the fingerprint sensor in accordance with the present invention.

[0025] With reference to FIG. 1, a display device 10 of the present invention has a display panel 11, an image driving unit 12, a touch sensing unit 20 and a power circuit 13. The image driving unit 12 has a gate driving unit 121 and a data driving unit 122. The gate driving unit 121, the data driving unit 122 and the touch sensing unit 20 are electrically connected to the display panel 11. The power circuit 13 respectively supplies voltages to the gate driving unit 121, the data driving unit 122 and the touch sensing unit 20.

[0026] With further reference to FIGS. 1, 2A and 2B, the first embodiment of the display device 10 in accordance with the present invention is shown. The display panel 11 of the display device 10 has multiple gate lines G.sub.1.about.G.sub.m, multiple data lines D.sub.1.about.D.sub.n, multiple pixel electrodes 112, multiple thin-film transistors Q.sub.11.about.Q.sub.1n, Q.sub.21.about.Q.sub.2n . . . , Q.sub.m1.about.Q.sub.mn, multiple signal lines L.sub.1.about.L.sub.K and a common electrode layer 111. The gate lines G.sub.1.about.G.sub.m are electrically connected to the gate driving unit 121, the data lines D.sub.1.about.D.sub.n are electrically connected to the data driving unit 122. The gate lines G.sub.1.about.G.sub.m and data lines D.sub.1.about.D.sub.n are insulated and interlaced to each other to define multiple pixel areas. The pixel areas are arranged in a matrix. As shown in FIG. 2B, each pixel electrode 112 and each thin-film transistor Q.sub.11.about.Q.sub.1n, Q.sub.21.about.Q.sub.2n . . . , Q.sub.m1.about.Q.sub.mn are disposed in the corresponding pixel area. A gate, a source and a drain of each thin-film transistor Q.sub.11.about.Q.sub.1n, Q.sub.21.about.Q.sub.2n . . . , Q.sub.m1.about.Q.sub.mn are sequentially, respectively and electrically connected to the corresponding gate line G1, G2 . . . , G.sub.m, data line D.sub.1, D.sub.2 . . . , D.sub.n and the pixel electrode 112 in the corresponding pixel area to constitute to one sub-pixel P.sub.11.about.P.sub.1n, P.sub.21.about.P.sub.2n . . . , P.sub.m1.about.P.sub.mn. The common electrode layer 111 and the pixel electrodes 112 are insulated and parallel to each other. In the first embodiment, three adjacent sub-pixels are constituted to one display pixel and respectively generate a red light, a green light and a blue light. Take a liquid crystal display device as an example, the pixel electrodes 112 of the three adjacent sub-pixels respectively correspond to a red filter area, a green filter area and a blue filter area of a color filter film. In the first embodiment, each display pixel at least has three pixel electrodes 112. When the display device 10 displays an image, the gate driving unit 121 sequentially drives the gate lines G.sub.1.about.G.sub.m to be turned on the thin-film transistor Q.sub.11.about.Q.sub.1n, Q.sub.21.about.Q.sub.2n . . . , Q.sub.m1.about.Q.sub.mn respectively and electrically connected to the driven gate line G.sub.1.about.G.sub.m. The thin-film transistor Q.sub.11.about.Q.sub.1n, Q.sub.21.about.Q.sub.2n . . . , Q.sub.m1.about.Q.sub.mn driven to be turned on passes a display signal V.sub.d1.about.V.sub.dn outputted from the data driving unit 122 to the corresponding pixel electrode 112 through the corresponding data line D.sub.1.about.D.sub.n. The display signal determines that the pixel electrode 112 connected to the thin-film transistor Q.sub.11.about.Q.sub.1n, Q.sub.21.about.Q.sub.2n . . . , Q.sub.m1.about.Q.sub.mn driven to be turned on generates a specific gray level or color for displaying the image.

[0027] In the first embodiment, the common electrode layer 111 is divided into multiple common electrodes C.sub.1.about.C.sub.K arranged in a matrix. The common electrodes C.sub.1.about.C.sub.K are respectively and electrically connected to the touch sensing unit 20 through the corresponding signal lines L.sub.1.about.L.sub.K. Each of the common electrodes C.sub.1, C.sub.2 . . . , C.sub.K corresponds to h sub-pixels and h is an integer and larger than one (h>1). To further clearly and easily describe more details of the first embodiment, a common electrode C.sub.1 shown in FIG. 2A is used as an example. The common electrode C.sub.1 corresponds to nine pixel electrodes P.sub.11.about.P.sub.33 and h is equal to 9 (h=9) in the first embodiment. However, an amount of the pixel electrodes corresponding to each common electrode is determined according to a real display resolution of the display panel and a size of the common electrode for a real touch resolution. Preferably, the size of each common electrode matches a size of a single sensing electrode of an individual touch panel.

[0028] With reference to FIGS. 1 and 2B, in the first embodiment, the touch sensing unit 20 has a controller 21 and multiple sensing circuits 22, and also has multiple analog to digital converters 23. The sensing circuits 22 are electrically connected to the controller 21 and respectively connected to the corresponding common electrodes C.sub.1.about.C.sub.K through the signal lines L.sub.1.about.L.sub.K to sense a signal V.sub.pen emitted from an active stylus.

[0029] With reference to FIG. 2B, an embodiment of the sensing circuit 22 has a charge sharing circuit 221 and a multiplexer 222. A first input (-) of the charge sharing circuit 221 is connected to the corresponding signal line L.sub.1 through a first switch S.sub.tp, so the first input (-) is coupled to the corresponding common electrode C.sub.1. A second input (+) of the charge sharing circuit 221 is connected to a common terminal com of the multiplexer 222 and an output O/P of the charge sharing circuit 221 outputs a sensing signal. Optionally, the output O/P may further output the sensing signal to the corresponding analog to digital converter 23. The analog to digital converter 23 converts the sensing signal to a specific digital data. A first switching terminal sw1 of the multiplexer 222 is connected to a common voltage Vcom of the power circuit 13 and a second switching terminal sw2 of the multiplexer 222 is connected to ground. The common voltage Vcom is a DC voltage. The charge sharing circuit 221 has an amplifier 223, a capacitor C.sub.fb and a second switch S.sub.fb. An inverting input (-) is used as the first input and a non-inverting input (+) is used as the second input. The capacitor C.sub.fb is connected to the inverting input (-) of the amplifier 223 and the output O/P of the charge sharing circuit 221. The second switch S.sub.fb is connected to the capacitor C.sub.fb in parallel. The first switch S.sub.tp, the multiplexer 222 and the second switch S.sub.fb are electrically connected to the controller 21. The controller 21 controls the first and second switches S.sub.tp, S.sub.fb to be turned on or turn off and also controls the common terminal com of the multiplexer 222 to selectively connect to the first and second switching terminals sw1, sw2.

[0030] With reference to FIGS. 1, 2B and 5, a flow chart of sensing the active stylus on the display device 10 in accordance with the present invention is further described as follows. The gate driving unit 121 and the data driving unit 122 of the display device 10 drive the sub-pixels P.sub.11.about.P.sub.1n, P.sub.21.about.P.sub.2n . . . , P.sub.m1.about.P.sub.mn to display images according to an image displaying period T_dis. As shown in FIG. 5, a duration of the image displaying period T_dis is divided into j time slots, wherein j is an integer and larger than one or equal to one. Each time slot is further divided into a displaying duration t_display and a touch sensing duration t_touch adjacent to the displaying duration t_display. The touch sensing duration t_touch can be defined before or after the displaying duration t_display. A display driving procedure is performed in the displaying duration t_display to drive each sub-pixel P.sub.11.about.P.sub.1n, P.sub.21.about.P.sub.2n . . . , P.sub.m1.about.P.sub.mn for displaying the image. The displaying duration t_display is divided into multiple pixel driving durations t.sub.D. In each pixel driving duration t.sub.D, the corresponding sub-pixel P.sub.11.about.P.sub.1n, P.sub.21.about.P.sub.2n . . . , P.sub.m1.about.P.sub.mn is driven to display the image. A touch sensing procedure is performed through the common electrodes C.sub.1.about.C.sub.K in the touch sensing duration t_touch to sense a touch object, such as a finger or an passive stylus, to obtain sensing information. In the first embodiment, each common electrode C.sub.1.about.C.sub.K is used as a touch sensing electrode S.sub.T1.about.S.sub.TK.

[0031] In each displaying duration t_display, the gate driving unit 121 sequentially outputs the gate driving signals V.sub.g1.about.V.sub.gm to the corresponding gate lines G.sub.1.about.G.sub.m. When the gate driving signal V.sub.g1 is outputted to the corresponding gate lines G.sub.1, the thin-film transistors Q.sub.11.about.Q.sub.1n connected to the gate line G.sub.1 is turned on. At the time, the data driving unit 122 provides the display signals V.sub.d1.about.V.sub.dn. The display signals V.sub.d1.about.V.sub.dn are provided to the pixel electrodes 112 through the turned-on thin-film transistors Q.sub.11.about.Q.sub.1n. In each displaying duration t_display, the three sub-pixels of the display pixel are driven to display the images at the same time or are sequentially driven to display the images according to different types of the display devices. Furthermore, the gate driving unit 121 outputs the gate driving signals V.sub.g1, V.sub.g2 . . . V.sub.gm to drive the sub-pixels of the display pixel to display the images and then stops outputting the gate driving signals V.sub.g1, V.sub.g2 . . . V.sub.gm after the images are completely formed at the same time, or stops outputting the gate driving signals V.sub.g1, V.sub.g2 . . . V.sub.gm after the images are completely formed in sequence. Take the first sub-pixel P.sub.11 in FIG. 2B as an example, when the gate driving unit 121 outputs the gate driving signal V.sub.g1 to the gate line G.sub.1 connected to the corresponding thin-film transistor Q.sub.11, the thin-film transistor Q.sub.11 is turned on and then the display signal V.sub.d1 on the corresponding data line D.sub.1 is provided to the pixel electrode 112 connected to the turned-on thin-film transistor Q.sub.11. At the time, the controller 21 of the touch sensing unit 20 controls the sensing circuit 22 which is connected to the common electrode corresponding to the first sub-pixel P.sub.11. That is, the controller 21 outputs a control signal V.sub.mux to the multiplexer 222 of the sensing circuit 22 and the common terminal com of the multiplexer 222 is then connected to the first switching terminal sw1 to provide the common voltage V.sub.com to the common electrode C.sub.1 corresponding to the first sub-pixel P.sub.11. In the liquid crystal display device, a liquid crystal layer has multiple liquid crystals and is sandwiched in between the pixel electrode 112 and common electrode C.sub.1 corresponding to the pixel electrode 112. When the display signal V.sub.d1 is provided to the pixel electrode 112 and the common electrode C.sub.1 is connected to the common voltage V.sub.com. At the same time, the liquid crystals start to rotate and change their directions. When a voltage of the pixel electrode 112 reaches a target value, the liquid crystals rotate to a target direction and the first sub-pixel P.sub.11 starts to display the image. In the displaying duration t_display, the present invention senses the signal V.sub.pen of the active stylus through the common electrode C.sub.1. That is, in the displaying duration t_display, the signal can be sensed by the common electrode C.sub.1 when the voltage V.sub.pixel of the pixel electrode 112 corresponding to the common electrode C.sub.1 is in a stable voltage range defined between an upper voltage V.sub.H1 and a lower voltage V.sub.H2, as shown in FIG. 6B.

[0032] With reference to FIG. 6A, a voltage waveform of the display signal V.sub.d provided by the data driving unit 122 is shown. When the gate line G.sub.1 of the first sub-pixel P.sub.11 is driven at a time point t1, the thin-film transistor Q.sub.11 of the first sub-pixel P.sub.11 turns on. At that time, the display signal V.sub.d1 on the data line D.sub.1 connected to the thin-film transistor Q.sub.11 is provided to the pixel electrode 112 of the first sub-pixel P.sub.11. The voltage of the display signal V.sub.d1 continuously changes from a positive voltage V.sub.H to a negative voltage V.sub.L. In the first embodiment, when the thin-film transistor Q.sub.1 of the first sub-pixel P.sub.11 is driven to be turned on, the voltage of the display signal V.sub.d1 is the positive voltage V.sub.H. A voltage level of the display signal V.sub.d1 starts to rise from a starting voltage and then reaches a target voltage after a first period of time t.sub.d1. For example, if the first sub-pixel P.sub.11 is driven to display a white image, as shown in FIG. 6A, the target voltage of the first sub-pixel P.sub.11 is set to a VDD. After a second period of time t.sub.d2, the voltage level of the display signal V.sub.d1 starts to decrease from the target voltage back to the starting voltage. And then, the voltage level of the display signal V.sub.d1 reaches the starting voltage after a third period of time t.sub.EQ. In the first embodiment, the starting voltage of the display signal V.sub.d1 is the same as the common voltage, but is not limited thereto.

[0033] With further reference to FIG. 6B, FIG. 6B is a voltage waveform diagram showing a voltage change of the pixel electrode 112 of the first sub-pixel P.sub.11. The liquid crystals between the pixel electrode 112 and the common electrode C1 start to rotate when the voltage level of the display signal V.sub.d1 starts to change, and then the liquid crystals rotate to a target angle after the second period of time t.sub.d2. At the time, the first sub-pixel P.sub.11 completely displays the corresponding image and the voltage change of the present voltage level of the pixel electrode 112 is in a voltage undulation range. That is, the voltage V.sub.pixel of the pixel electrode 112 reaches to the stable voltage range (V.sub.H1.about.V.sub.H2). The voltage undulation range is determined according to a voltage undulation range that does not affect the sensing signal generated by detecting the signal V.sub.pen of the active stylus. Furthermore, during a third period of time t.sub.EQ, the voltage level of the display signal V.sub.d1 decreases from the target voltage to the starting voltage. The gate line G.sub.1 of the first sub-pixel P.sub.11 is not driven in the third period of time t.sub.EQ, so the voltage V.sub.pixel of the pixel electrode 112 is maintained in the stable voltage range (V.sub.H1.about.V.sub.H2). In the first embodiment, during the displaying duration t_display, there are two durations when the voltage V.sub.pixel of the pixel electrode 112 is maintained in the stable voltage range. One of the two durations is a first detection duration t.sub.P1 starting at a time point when the voltage V.sub.pixel of the pixel electrode 112 of the first sub-pixel P.sub.11 reaches to the stable voltage range after the first pixel sub-pixel P.sub.11 is driven and ending at a time point when the first sub-pixel P.sub.11 is not driven anymore. The other duration is a second detection duration t.sub.P2 starting at the end time of the first detection duration t.sub.P1 and ending at an end time of the pixel driving duration T.sub.D, that is the second detection duration t.sub.P2 corresponds to the third period of time t.sub.EQ. The sensing circuit 22 senses the signal V.sub.pen of the active stylus through the common electrode C.sub.1 during the first and/or second detection durations t.sub.p1, t.sub.p2.

[0034] In addition, the gate driving unit 121 requires an initial preparation period t.sub.P3 (or so called a pre-charging period) for the first sub-pixel P.sub.11 to be turned on when the gate line G.sub.1 of the first sub-pixel P.sub.11 is driven at the time point t1. In the initial preparation period t.sub.p3, the first sub-pixel P.sub.11 is not turned on until a target gate voltage on the gate line G.sub.1 is reached. Therefore, the voltage V.sub.pixel of the pixel electrode 112 of the first sub-pixel P.sub.11 is maintained at the common voltage level and is kept in the stable voltage range, too. In other words, the voltage V.sub.pixel of the pixel electrode 112 is maintained in the stable voltage range during the initial preparation period t.sub.P3, so the present invention can sense the signal V.sub.pen of the active stylus through the common electrode C.sub.1 in the initial preparation period t.sub.P3. Here, the initial preparation period t.sub.P3 is a third detection of time t.sub.P3. Therefore, in the displaying duration t_display, the signal V.sub.pen of the active stylus can be sensed by the common electrode C.sub.1 when the voltage V.sub.pixel of the pixel electrode 112 corresponding to the common electrode C.sub.1 keeps in the stable voltage range. In the first embodiment, the initial preparation period t.sub.P3 overlaps but is less than the first period of time t.sub.d1, and starts at a starting time of the pixel driving time T.sub.D and ends before a time when the voltage V.sub.pixel of the pixel electrode 112 of the first sub-pixel P.sub.11 starts to change.

[0035] The multiple sub-pixels P.sub.11.about.P.sub.1n, P.sub.21.about.P.sub.2n . . . , P.sub.m1.about.P.sub.mn respectively display different color images according to different voltages of the display signals V.sub.d1.about.V.sub.dn respectively provided to the multiple sub-pixels P.sub.11.about.P.sub.1n, P.sub.21.about.P.sub.2n . . . , P.sub.m1.about.P.sub.mn. That is, the target values for the pixel electrodes 112 of the sub-pixels P.sub.11.about.P.sub.in, P.sub.21--P.sub.2n . . . , P.sub.mi-P.sub.mn displaying different color images are different, too. Therefore, after the sub-pixels P.sub.11.about.P.sub.1n, P.sub.21.about.P.sub.2n . . . , P.sub.m1.about.P.sub.mn are driven, raising times from the starting voltages thereof respectively to the corresponding target values are different, so the first and the second detection durations t.sub.P1, t.sub.P2 of the sub-pixels P.sub.11.about.P.sub.1n, P.sub.21.about.P.sub.2n . . . , P.sub.m1.about.P.sub.mn are different, too. Therefore, the starting times of the first detection durations t.sub.P1 for different sub-pixels P.sub.11.about.P.sub.1n, P.sub.21.about.P.sub.2n . . . , P.sub.m1.about.P.sub.mn are different when the display signals V.sub.d1.about.V.sub.dn with different voltages or different target values are provided to the corresponding sub-pixels P.sub.11.about.P.sub.1n, P.sub.21.about.P.sub.2n . . . , P.sub.m1.about.P.sub.mn. In one embodiment, the sensing circuit 22 may determine the starting times of the first detection durations tpl of all of the sub-pixels P.sub.11.about.P.sub.1n, P.sub.21.about.P.sub.2n . . . , P.sub.m1.about.P.sub.mn according to the voltages of the display signals V.sub.d1.about.V.sub.dn respectively obtained by the currently-driven sub-pixels P.sub.11.about.P.sub.1n, P.sub.21.about.P.sub.2n . . . , P.sub.m1.about.P.sub.mn. In another embodiment, the sensing circuit 22 may determine a common first detection duration t.sub.P1 for all sub-pixels P.sub.11.about.P.sub.1n, P.sub.21.about.P.sub.2n . . . , P.sub.m1.about.P.sub.mn, wherein the common first detection t.sub.P1 is determined according to the raising time (charging time) of a highest stable voltage V.sub.Hmax of the pixel electrode 112 or a falling time (discharging time) of a lowest stable voltage V.sub.Lmin of the pixel electrode 112. That is, regardless of a magnitude of the voltage or the target value of the display signals V.sub.d1.about.V.sub.dn obtained by the currently-driven sub-pixels P.sub.11.about.P.sub.1n, P.sub.21.about.P.sub.2n . . . , P.sub.m1.about.P.sub.mn, the starting time of the common first detection duration t.sub.P1 is the time when the voltage V.sub.pixel of the pixel electrode 112 of each of the currently-driven sub-pixels P.sub.11.about.P.sub.1n, P.sub.21.about.P.sub.2n . . . , P.sub.m1.about.P.sub.mn in the pixel driving duration t.sub.D has been in the stable voltage range. Accordingly, no matter what color images are displayed by the driven sub-pixels P.sub.11.about.P.sub.1n, P.sub.21.about.P.sub.2n . . . , P.sub.m1.about.P.sub.mn, each of the sensing circuits 22 may sense the signal V.sub.pen of the active stylus when the voltage V.sub.pixel of the pixel electrode 112 of each of the currently-driven sub-pixels P.sub.11.about.P.sub.1n, P.sub.21.about.P.sub.2n . . . , P.sub.m1.about.P.sub.mn is in the stable voltage range.

[0036] With reference to FIGS. 2B, 5, 6A and 6B, the first, second and third detection durations t.sub.P1, t.sub.P2, t.sub.P3 are in the displaying duration t_display, so the present invention senses the signal V.sub.pen of the active stylus during the voltage V.sub.pixel of the pixel electrode 112 of the first sub-pixel P.sub.11 in the stable voltage range. That is, when the active stylus approaches to the common electrode C.sub.1 corresponding to the first sub-pixel P.sub.11, a capacitor C.sub.pen is electrically coupled between the active stylus and the common electrode C.sub.1. At the same time, the signal V.sub.pen of the active stylus changes an amount of charges in the capacitor C.sub.pen and the sensing circuit 22 which is electrically connected to the common electrode C.sub.1 may sense the signal V.sub.pen of the active stylus accordingly. Particularly, to avoid an interference from the display signal V.sub.d1 provided to the first sub-pixel P.sub.11, the controller 21 controls the sensing circuit 22 that senses an approach of the active stylus in the first, second and/or initial preparation durations t.sub.P1, t.sub.P2, t.sub.P3.

[0037] With reference to FIGS. 5, 6A and 6B, in the displaying duration t_display, the controller 21 controls the first switch S.sub.tp to be turned on and to electrically connect the sensing circuit 22 and the common electrode C.sub.1. The second switch S.sub.fb is also controlled to be turned on by the controller 21 to remove the charges in the capacitor C.sub.fb. At the time, the common terminal com of the multiplexer 222 is connected to the first switching terminal sw1. However, in the first, second and/or initial preparation durations t.sub.P1, t.sub.P2, t.sub.P3, the controller 21 controls the second switch S.sub.fb to turn off. At the same time, if the active stylus approaches to the common electrode C.sub.1, as shown in FIG. 2B, the signal V.sub.pen of the active stylus changes the amount of charges in the capacitor C.sub.pen between them. Since the first switch S.sub.tp turns on but the second switch S.sub.fb turns off, the charges in the capacitor C.sub.pen are transferred to the capacitor C.sub.fb of the charge sharing circuit 221. The amplifier 223 outputs the sensing signal to the corresponding analog to digital converter 23 based on the amount of charges in the capacitor C.sub.fb. Therefore, the approach of the active stylus to the first sub-pixel P.sub.11 may be determined.

[0038] In each displaying duration t_display, a first sub-pixel P.sub.11 is selected to be driven. The voltage V.sub.pixel of the pixel electrode 112 of the selected first sub-pixel P.sub.11 is maintained in the stable voltage range during the first, second and initial preparation durations t.sub.P1, t.sub.P2, t.sub.P3, so the present invention can sense the signal V.sub.pen of the active stylus by the common electrode C.sub.1 corresponding to the driven first sub-pixel P.sub.11 in the first, second and initial preparation durations t.sub.P1, t.sub.P2, t.sub.P3.

[0039] With reference to FIGS. 1, 2B and 5, a touch scanning procedure is executed in the touch sensing duration t_touch to obtain touch information by sensing a touch object, such as a finger or a passive stylus. In the touch sensing duration t_touch, the gate driving unit 121 does not output the gate signal V.sub.g1.about.V.sub.gm to the thin-film transistors Q.sub.11.about.Q.sub.1n, Q.sub.21.about.Q.sub.2n . . . , Q.sub.m1.about.Q.sub.mn and the data driving unit 122 does not output the display signal V.sub.d1.about.V.sub.dn to the thin-film transistors Q.sub.11.about.Q.sub.1n, Q.sub.21.about.Q.sub.2n . . . , Q.sub.m1.about.Q.sub.mn, either. The touch sensing duration t_touch has a driving phase t.sub.E and a sensing phase t.sub.S. Each of the sensing circuit 22 further has a third switch S.sub.P electrically connected to the signal line L.sub.1 of the sensing circuit 22 and a driving voltage VDD. As shown in FIG. 5, in the driving phase T.sub.E of the touch sensing duration t_touch, the controller 21 outputs a control signal V.sub.mux to the multiplexer 222 of the sensing circuit 22 to connect the common terminal com to the second switching terminal sw2, so the second input (+) of the amplifier 223 is connected to ground. At the same time, the second switch S.sub.fb and the third switch S.sub.P are controlled to be turned on and the first switch S.sub.tp is controlled to be turned off, so the driving voltage VDD is supplied to the common electrode C.sub.1 which is connected to the sensing circuit 22. At the same time, as shown in FIG. 7, if the finger or the passive stylus approaches to the common electrode C.sub.1, a capacitor C.sub.F is electrically coupled between them. Next go to the sensing phase T.sub.S, the controller 21 controls the second switch S.sub.fb and the third switch S.sub.P to be turned off and keeps the first switch St.sub.P in a turn-off status, so the charges in the capacitor C.sub.F are transferred to the capacitor C.sub.fb of the charge sharing circuit 221. The output O/P of the amplifier 223 outputs the sensing signal corresponding to the amount of charges in the capacitor C.sub.fb and the sensing signal is used as the touch information. Therefore, the charge sharing circuit 221 senses the approach or the touch of a finger or passive stylus through the common electrode C.sub.1.

[0040] Based on the foregoing description, the first embodiment of the display device 10 in accordance with the present invention can sense the active stylus during the display panel 11 displays the images. In other words, the active stylus sensing procedure of the present invention is not performed in the touch sensing duration t_touch for performing the touch sensing procedure. Therefore, the displaying duration t_display is not shortened to perform the active stylus sensing procedure and the quality of displaying image is not affected. Similarly, the touch sensing duration t_touch is not divided into another duration to sense the active stylus, so the accuracy of sensing the touch object is not affected.

[0041] With reference to FIG. 3A, a second embodiment of the display device 10 of the present invention is shown and is similar to the first embodiment. In the second embodiment, each of the common electrodes C.sub.1.about.C.sub.K of the first embodiment is further divided into multiple common electrodes C.sub.11.about.C.sub.mn, each of which corresponds to one sub-pixel P.sub.11.about.P.sub.1n, P.sub.21.about.P.sub.2n . . . , P.sub.m1.about.P.sub.mn. Relatively, the second embodiment requires more signal lines L.sub.1.about.L.sub.K and sensing circuit 22, as shown in FIG. 1. With reference to FIGS. 3B and 5, in the second embodiment, a controlling procedure of the controller 21 in first, second and initial detection durations t.sub.P1, t.sub.P2, t.sub.P3 of the displaying duration t_display is the same as that of the first embodiment, so the same controlling procedure is not necessary to describe here. In the second embodiment, each of the common electrodes C.sub.11.about.C.sub.mn is also individually used as a touch sensing electrode. In comparison with the first embodiment, an accuracy and resolution of sensing the active stylus or the touch object are increased, since the common electrode layer 111' is further divided into more common electrodes C.sub.11.about.C.sub.mn corresponding to the sub-pixels P.sub.11.about.P.sub.1n, P.sub.21.about.P.sub.2n . . . , P.sub.m1.about.P.sub.mn in the second embodiment. Such structure of the second embodiment may be used in different applications.

[0042] With reference to FIG. 4A, a third embodiment of the display device 10 of the present invention is shown. Similar to the second embodiment, in the third embodiment, the common electrode layer 111'' is also divided into more common electrodes C.sub.11.about.C.sub.mn and each of the common electrodes C.sub.11.about.C.sub.mn corresponds to one of the sub-pixels P.sub.11.about.P.sub.1n, P.sub.21.about.P.sub.2n . . . , P.sub.m1.about.P.sub.mn, but one common electrode C.sub.11, C.sub.12 . . . , C.sub.mn is not individually used as a touch sensing electrode S.sub.T1.about.S.sub.TK. Each of the touch sensing electrodes S.sub.T1.about.S.sub.TK of the third embodiment has h common electrodes adjacent to each other, which are arranged in a matrix and are electrically connected to each other, wherein h is an integer and larger than one (h>f1). For example, the common electrodes C.sub.11.about.C.sub.33 are electrically connected in serial to use as the touch sensing electrode S.sub.T1. With reference to FIGS. 1 and 4B, in the display panel 11, the common electrodes C.sub.11.about.C.sub.33 are electrically connected in serial. The sensing circuits 22 are respectively and electrically connected to the common electrode C.sub.11.about.C.sub.mn of the corresponding touch sensing electrodes S.sub.T1.about.S.sub.TK through the corresponding signal line L.sub.1.about.L.sub.K. That is, the sensing circuit 22 is electrically connected to all of the common electrodes C.sub.11.about.C.sub.33 of the corresponding touch sensing electrode S.sub.T1 through the signal line L.sub.1. With further reference to FIGS. 4B and 5, in the third embodiment, the controlling procedure of the controller 21 executed in the first, second and initial detection durations t.sub.P1, T.sub.P2, t.sub.P3 of the displaying duration t_display is the same as that of the first embodiment, so the same controlling procedure is not necessary to describe here. In the third embodiment, the amount of charges in the capacitor C.sub.fb of the charge sharing circuit 223 are transferred from all of the common electrodes C.sub.11.about.C.sub.33 of the corresponding touch sensing electrode S.sub.T1, so the charge sharing circuit 223 senses the charge change of all of the common electrodes C.sub.11.about.C.sub.33 of the corresponding touch sensing electrode S.sub.T1. Furthermore, an amount of the common electrodes (h) may be determined according to the size of a touch sensing electrode. Therefore, the present invention also has a better design margin for practical adjustment of the desired resolution.

[0043] Based on the foregoing embodiments, a method for sensing the active stylus is performed in the displaying duration for displaying image, but not in the touch sensing duration for sensing the touch object. As a result, the displaying duration is not shortened to perform the active stylus sensing procedure and the quality of displaying image is not affected. Similarly, the touch sensing duration is not divided into another duration to sense the active stylus and the accuracy of sensing the touch object is not affected.

[0044] Even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with the details of the structure and features of the invention, the disclosure is illustrative only. Changes may be made in the details, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.

Claims

1. A method for sensing an active stylus on a display device, wherein the display device comprises multiple sub-pixels and multiple common electrodes respectively corresponding to at least one of the sub-pixels, and the method comprises: sensing a signal of an active stylus through one of the common electrodes for displaying an image in a displaying duration of the display device.

2. The method as claimed in claim 1, wherein the displaying duration has a pixel driving duration, and in the pixel driving duration, one of the sub-pixels having a pixel electrode is driven for displaying the image, and the common electrode corresponding the driven sub-pixel is used to sense the signal of the active stylus when a voltage of the pixel electrode is in a stable voltage range; wherein the stable voltage range is defined bewteen an upper voltage and a lower voltage.

3. The method as claimed in claim 2, the pixel driving duration having a first detection duration, wherein in the first detection duration, the common electrode which corresponds to the driven sub-pixel is used to sense the signal of the active stylus, wherein the first detection duration starts at a first time when the voltage of the pixel electrode of the driven sub-pixel reaches to the stable voltage range and ends at a second time when the driven sub-pixel is not driven.

4. The method as claimed in claim 3, the pixel driving duration further has a second detection duration, wherein in at least one of the first and second detection durations, the common electrode corresponding to the driven sub-pixel is used to sense the signal of the active stylus, wherein the second detection duration starts at an end time of the first detection duration and ends at an end time of the pixel driving duration.

5. The method as claimed in claim 2, the pixel driving duration has a third detection duration, wherein in the third detection duration, the common electrode corresponding to the driven sub-pixel is used to sense the signal of the active stylus, wherein the third detection duration starts at a starting time of the pixel driving duration and ends at a time point when the voltage of the pixel electrode of the driven sub-pixel starts to change.

6. The method as claimed in claim 2, wherein each of the common electrodes of the display device respectively corresponds to one of the sub-pixels having the pixel electrode, and a plurality of the common electrodes adjacent to each other are electrically connected in serial to use as a touch sensing electrode, wherein in the displaying duration, at least one of the sub-pixels having the pixel electrode is driven and the touch sensing electrode including at least one of the common electrodes corresponding to the at least one driven sub-pixel is used to sense the signal of the active stylus when the voltage of the pixel electrode of the at least one driven sub-pixel reaches to the stable voltage range.

7. The method as claimed in claim 1, further comprising a touch sensing duration of the display device adjacent to the displaying duration, wherein in the touch sensing duration, a driving voltage is outputted to the common electrodes and touch information obtained by sensing a touch object through the common electrodes is outputted.

8. The method as claimed in claim 1, wherein in the displaying duration, the common electrode for displaying the image is connected to a common voltage and the common voltage is a DC voltage.

9. A device for sensing active stylus, electrically connected to a display device having multiple sub-pixels, multiple common electrodes respectively corresponding to at least one of the sub-pixels and an image driving unit electrically connected to the sub-pixels, wherein the device for sensing active stylus comprises: a touch sensing unit electrically connected to the common electrodes, wherein in a displaying duration of the display device, the image driving unit drives one of the sub-pixels to display an image and the touch sensing unit senses a signal of an active stylus through one of the common electrodes corresponding to the driven sub-pixel.

10. The device as claimed in claim 9, the displaying duration having at least one pixel driving duration, wherein in the pixel driving duration, when the image driving unit drives one of the sub-pixels having a pixel electrode to display the image, the touch sensing unit senses the signal of the active stylus through the common electrode corresponding the driven sub-pixel when a voltage of the pixel electrode of the driven sub-pixel is in a stable voltage range; wherein the stable voltage range is defined between an upper voltage and a lower voltage.

11. The device as claimed in claim 10, the pixel driving duration having a first detection duration, wherein in the first detection duration, the touch sensing unit senses the signal of the active stylus through the common electrode corresponding to the driven sub-pixel, wherein the first detection duration starts at a first time when the voltage of the pixel electrode of the driven sub-pixel reaches the stable voltage range and ends at a second time when the driven sub-pixel is not driven.

12. The device as claimed in claim 11, wherein the pixel driving duration further has a second detection duration, wherein in at least one of the first and second detection durations, the touch sensing unit senses the signal of the active stylus through the common electrode corresponding to the driven sub-pixel, wherein the second detection duration starts at an end time of the first detection duration and ends at an end time of the pixel driving duration.

13. The device as claimed in claim 10, wherein the pixel driving duration has a third detection duration, wherein in the third detection duration, the touch sensing unit senses the signal of the active stylus through the common electrode corresponding to the driven sub-pixel, wherein the third detection duration starts at a starting time of the pixel driving duration and ends at a time point when the voltage of the pixel electrode of the driven sub-pixel starts to change.

14. The device as claimed in claim 10, wherein the touch sensing unit presets a common first detection duration, wherein the common first detection duration is determined according to a charging time required by a highest stable voltage or a discharging time required by a lowest stable voltage.

15. The device as claimed in claim 11, wherein each of the common electrodes respectively corresponds to one of the sub-pixels and a plurality of the common electrodes adjacent to each other are electrically connected in serial to use as a touch sensing electrode for sensing the signal of the active stylus.

16. The device as claimed in claim 11, the touch sensing unit comprising a controller and multiple sensing circuits electrically connected to the controller, the sensing circuits respectively and electrically connected to the common electrodes, wherein each of the sensing circuit comprises: a charge sharing circuit having a first input, a second input and an output, wherein the first input is connected to the common electrode corresponding to the sensing circuit through a first switch, the second input is selectively connected to a common voltage or a ground, and the output outputs a sensing signal corresponding to the signal of the active stylus; wherein the charge sharing circuit and the first switch are respectively connected to controller and in the displaying duration, the controller controls the charge sharing circuit to connect the second input to the common voltage and turns on the first switch to connect electrically the first input of the charge sharing circuit to the common electrode corresponding to the sensing circuit.

17. The device as claimed in claim 16, the charge sharing circuit comprising: an amplifier having an inverting input and a non-inverting input; a capacitor connected between the inverting input and the output; and a second switch connected to the capacitor in parallel and electrically connected to the controller, wherein the controller controls the second switch to turn off in the displaying duration.

18. The device as claimed in claim 17, wherein the touch sensing unit outputs a driving voltage to the common electrodes in a touch sensing duration adjacent to the displaying duration and outputs touch information after sensing a touch object through the common electrodes.

19. The device as claimed in claim 18, wherein the charge sharing circuit further comprises a third switch connected between the driving voltage and the common electrode corresponding to the sensing circuit, wherein the third switch is electrically connected to the controller, wherein the touch sensing duration has a driving phase and a sensing phase, wherein in the driving phase, the controller controls the third switch to be turned on to provide the driving voltage to the common electrode corresponding the turned-on third switch, the first switch to turn off and the second switch to be turned on at the same time; and in the sensing phase, the controller controls the third switch to turn off, the first switch to be turned on and the second switch to turn off at the same time.

20. The device as claimed in claim 16, the common voltage is a DC voltage.